Magnetic impedance device, sensor apparatus using the same and method for manufacturing the same

ABSTRACT

A magnetic sensor apparatus includes a semiconductor substrate and a magnetic impedance device for detecting a magnetic field. The magnetic impedance device is disposed on the substrate. The magnetic sensor apparatus has minimum size and is made with low manufacturing cost. Here, the magnetic impedance device detects a magnetic field in such a manner that impedance of the device is changed in accordance with the magnetic filed when an alternating current is applied to the device and the impedance is measured by an external electric circuit.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Applications No.2002-337416 filed on Nov. 21, 2002, No. 2002-337417 filed on Nov. 21,2002, No. 2003-58899 filed on Mar. 5, 2003, No. 2003-58900 filed on Mar.5, 2003, and No. 2003-73900 filed on Mar. 18, 2003, the disclosures ofwhich are incorporated herein by reference.

[0002] 1. Field of the Invention

[0003] The present invention relates to a magnetic impedance device, asensor apparatus using the same and a method for manufacturing the same.The sensor apparatus is suitably used for a rotation sensor apparatus.

[0004] 2. Background of the Invention

[0005] A conventional magnetic impedance device utilizes a magneticimpedance effect, and is disclosed in Japanese Patent ApplicationPublication No. H08-75835. The magnetic impedance effect is thatimpedance of the device changes in accordance with an outside stress ina case where the device is energized with an alternating current (e.g.,a high frequency alternating current, the frequency being higher than 1MHz). The device includes a magnetic layer, which is made of amorphousalloy and has a soft magnetic property. Here, the amorphous alloy hashigh relative magnetic permeability. Therefore, a change of the magneticpermeability in the magnetic layer in accordance with an externalmagnetic field becomes large, so that the device has high sensitivity.

[0006] However, the magnetic impedance device with the magnetic layermade of amorphous alloy has low heat resistance, so that the sensitivityof the device is much decreased in a case where the device is processedwith heat treatment above almost 400° C. The reason is as follows. Thecrystallization temperature of the magnetic layer made of amorphousalloy is low, i.e., at around 400° C. Therefore, when the device isprocessed with heat treatment above almost 400° C., the amorphous alloyis crystallized, so that the soft magnetic property of the amorphousalloy disappears. Here, the soft magnetic property of the amorphousalloy provides high sensitivity magnetic impedance.

[0007] Further, in a case where the magnetic layer is formed of easilyoxidizable material, the magnetic layer is oxidized with heat treatment,so that the soft magnetic property is deteriorated. Thus, thesensitivity is decreased.

[0008] Therefore, it is difficult to manufacture the magnetic impedancedevice having the magnetic layer made of amorphous alloy with using aconventional semiconductor processing method. That is because theconventional method usually includes a step of heat treatment abovealmost 400° C. Accordingly, it is difficult to minimize the device withusing the conventional method so that the device is integrated withanother circuit such as a sensor output signal processor.

[0009] Further, when the device is annealed, i.e., processed with heattreatment, a stress is generated in a substrate since thermal expansionof the substrate is different from that of the device. Here, the deviceis mounted on the substrate. Therefore, in some cases, the device may beremoved from the substrate. To prevent from being removed, depositioncondition for depositing a magnetic layer composing a magnetic impedancedevice is changed, or a film quality of the magnetic layer is changed.This is disclosed in Japanese Patent Application PublicationNo.2001-228229. However, this device is necessitated to form withlimited manufacturing method and to have a limited construction.

[0010] Moreover, since a magnetic impedance device having highsensitivity is available for various sensor systems, minimization andlow manufacturing cost are much required. For example, a magneticimpedance head module according to a prior art having a thin filmmagnetic impedance device is disclosed in Japanese Patent ApplicationPublications No.2001-318131. The head module includes the thin filmmagnetic impedance device, an electric power supply circuit forenergizing the device with a high frequency alternating current, and adetection circuit for detecting a impedance change, which are providedwith a discrete circuit. And each discrete circuit is combined with ahybrid IC. Therefore, minimization and reduction of manufacturing costof the head module are limited.

[0011] Further, a magnetic impedance device is suitably used for asensor apparatus mounted on an automotive vehicle, the sensor apparatusdetecting, for example, rotation of a rotational body. A rotation sensorapparatus according to a prior art is disclosed in Japanese PatentApplications No. H08-304432 (i.e., U.S. Pat. No. 5,841,276) and No.2000-46513. These sensor apparatuses are mounted on an engine of avehicle or on a wheel hub, so that the sensor apparatuses detectrotation of crankshaft of the engine or rotation of wheel of thevehicle, respectively. In each case, it is required to minimize thesensor apparatus so as to improve mounting performance of the apparatusand to increase design freedom of an engine and so on.

[0012] Further, the magnetic impedance device mounted on the vehicle isrequired to be protected from outside disturbance of magnetic field withusing a simple construction of the device. That is because the magneticimpedance device has high sensitivity so that the device is easilyaffected by the outside disturbance of magnetic field. Therefore, acurrent sensor having a magnetic impedance device according to a priorart, for example, includes a magnetic shield and a pair of reverse woundcoil for reducing the outside disturbance. This type of current sensoris disclosed in Japanese Patent Application Publication No. 2001-116773.However, this current sensor has a complicated construction so that amanufacturing cost is increased.

SUMMARY OF THE INVENTION

[0013] In view of the above problem, it is an object of the presentinvention to provide a sensor apparatus having a magnetic impedancedevice, which has minimum size and is made with low manufacturing cost.Specifically, the magnetic impedance device has high heat resistance.Namely, magnetic property of the device, i.e., sensor sensitivity is notdecreased even when the device is processed with heat treatment. Morespecifically, the sensor apparatus is suitably used for a rotationsensor having high mounting performance and high design freedom.

[0014] It is another object of the present invention to provide a methodfor manufacturing the above sensor apparatus with a magnetic impedancedevice, which has minimum size and is made with low manufacturing cost.

[0015] It is further another object of the present invention to providea sensor apparatus having a magnetic impedance device, which has highresistance against an outside disturbance of magnetic field.Specifically, the sensor apparatus is suitably used for a rotationsensor mounted, for example, on an automotive vehicle.

[0016] A magnetic sensor apparatus includes a semiconductor substrateand a magnetic impedance device for detecting a magnetic field. Themagnetic impedance device is disposed on the substrate. This magneticsensor apparatus has minimum size and is made with low manufacturingcost.

[0017] Further, a method for manufacturing the above magnetic sensorapparatus includes the steps of forming a stress relaxation layer on thesubstrate, and forming the magnetic impedance device on the stressrelaxation layer. The stress relaxation layer reduces a stress generatedin the substrate in a case where the apparatus is processed in a heattreatment. This method provides the magnetic sensor apparatus havingminimum size and being made with low manufacturing cost. Further, thereliability of the apparatus concerned with a mechanical strength isimproved.

[0018] Preferably, in the above apparatus, the magnetic impedance devicedetects a magnetic field in such a manner that impedance of the deviceis changed in accordance with the magnetic filed when an alternatingcurrent is applied to the device and the impedance is measured by anexternal electric circuit. The magnetic impedance device includes amagnetic layer made of Ni—Fe series alloy film. The magnetic layer has alength defined as L1 in an energization direction of the alternatingcurrent, a width defined as L2 in a perpendicular directionperpendicular to the energization direction, and a thickness of themagnetic layer defined as L3. The ratio of the length and the width isdefined as α, i.e., α=L1/L2, and the ratio of the width and thethickness is defined as β, i.e., β=L2/L3. The ratio α is equal to orlarger than 10, and the ratio β is in a range between 1 and 50. Thethickness L3 is equal to or larger than 5 μm.

[0019] In the above apparatus, the sensor sensitivity is not decreasedeven when the apparatus is processed with heat treatment. Thus, theapparatus has high heat resistance. Further, the apparatus has highsensor sensitivity.

[0020] Preferably, the apparatus further includes a protection layer forcovering the magnetic layer. The protection layer is made ofelectrically insulation material. More preferably, the protection layerhas a compression stress as an internal stress, the compression stressbeing equal to or smaller than 500 MPa. More preferably, the protectionlayer has a tensile stress as an internal stress, the tensile stressbeing equal to or smaller than 100 MPa. In the above apparatus, thesensor sensitivity is not decreased even when the apparatus is processedwith heat treatment. Thus, the apparatus has high heat resistance.Specifically, the magnetic layer of the apparatus is not substantiallyoxidized even when the apparatus is annealed. Further, the apparatus hashigh sensor sensitivity.

[0021] Further, a rotation sensor apparatus includes a rotation body forproviding a periodic change of intensity of magnetic field disposedaround the rotation body in accordance with rotation of the rotationbody, a magnetic sensor having a magnetic impedance device for detectingthe periodic change of the intensity of magnetic field so as to detectthe rotation of the rotation body, and a separation shield forseparating between the rotation body and the magnetic sensor. Themagnetic sensor detects the rotation of the rotation body through theseparation shield.

[0022] In the above rotation sensor apparatus, the magnetic sensorhaving high sensor sensitivity can detect the rotation of the rotationbody, even though the separation shield is disposed between the magneticsensor and the rotation body. Therefore, the magnetic sensor can bedisposed outside the separation shield without drilling an opening formounting the magnetic sensor. Thus, the apparatus has high mountingperformance for mounting the magnetic sensor on the separation shieldand high design freedom of the separation shield.

[0023] Preferably, the separation shield is a casing for covering therotation body. The magnetic sensor detects the rotation of the rotationbody disposed in the casing.

[0024] Preferably, the rotation sensor apparatus further includesanother magnetic sensor. The two magnetic sensors are arranged inparallel so as to separate by a half of pitch of the rotation body andsymmetrically disposed around a rotation axis of the rotation body. Thetwo magnetic sensors output signals, respectively, so that adifferential output signal is obtained. In this case, the apparatusdetects a differential output generated from both magnetic sensors. Thisdifferential output cancels a constant component of the geomagneticfield disposed in each magnetic sensor. Therefore, the apparatus detectsthe periodic change of magnetic field much accurately. Namely, theapparatus detects the rotation much accurately.

[0025] Preferably, the separation shield is a sensor casing for coveringthe magnetic sensor. The sensor casing is made of magnetic material andincludes an opening, which faces the rotation body. The magnetic sensordetects the rotation of the rotation body through the opening of thesensor casing. In this case, the apparatus has a simple construction insuch a manner that the sensor casing having the small opening covers themagnetic sensor so that the influence of disturbance of an externalmagnetic field around the magnetic sensor is reduced. Therefore, themanufacturing cost of the apparatus is reduced. Further, the apparatushaving the magnetic impedance device, which has high resistance againstan outside disturbance of magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objects, features and advantages of thepresent invention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

[0027]FIG. 1 is a plan view showing a magnetic impedance deviceaccording to a first embodiment of the present invention;

[0028]FIG. 2 is a cross-sectional view showing the device taken alongline II-II in FIG. 1;

[0029]FIG. 3 is a cross-sectional view showing the device taken alongline III-III in FIG. 1;

[0030]FIGS. 4A to 4C are cross-sectional views of the device explaininga manufacturing method of the device according to the first embodiment;

[0031]FIG. 5 is a graph showing a relationship between an externalmagnetic field Hext and impedance Z of the device according to the firstembodiment;

[0032]FIG. 6 is a graph showing a relationship between temperature T andtemperature drift of impedance Z−Zat25° C./Zat25° C. at zero magneticfield of the device according to the first embodiment;

[0033]FIG. 7 is a graph showing a relationship between temperature T andtemperature dependence of sensor sensitivity Δ (Z−Zat25° C./Zat25°C.)/(Z−Zat25° C./Zat25° C.) of the device according to the firstembodiment;

[0034]FIG. 8 is a table showing coefficients of temperature dependenceof the magnetic impedance Δ Zo/Δ T at zero magnetic field and of thesensor sensitivity Δ (Δ Z/Zo)/Δ T in different devices, according to thefirst embodiment;

[0035]FIG. 9 is a table showing the ratio of impedance change Δ Z/Zo indifferent devices, according to the first embodiment;

[0036]FIG. 10 is a graph showing a relationship between a length L1 ofthe magnetic layer and a ratio of impedance change Δ Z/Zo in the devicesaccording to the first embodiment;

[0037]FIG. 11 is a table showing the ratio of impedance change Δ Z/Zo indifferent devices, according to the first embodiment;

[0038]FIG. 12 is a graph showing a relationship between a width L2 ofthe magnetic layer and a ratio of impedance change Δ Z/Zo in the devicesaccording to the first embodiment;

[0039]FIG. 13 is a table showing the ratio of impedance change Δ Z/Zo indifferent devices, according to the first embodiment;

[0040]FIG. 14 is a graph showing a relationship between a thickness L3of the magnetic layer and a ratio of impedance change Δ Z/Zo in thedevices according to the first embodiment;

[0041]FIG. 15 is a table showing the ratio of impedance change Δ Z/Zo indifferent devices, according to the first embodiment;

[0042]FIG. 16 is a graph showing a relationship between a grain size ofthe magnetic layer and a ratio of impedance change Δ Z/Zo in the devicesaccording to the first embodiment;

[0043]FIG. 17 is a table showing the ratio of impedance change indifferent devices, according to the first embodiment;

[0044]FIG. 18 is a graph showing a relationship between a surfaceroughness of the substrate and a ratio of impedance change Δ Z/Zo in thedevices according to the first embodiment;

[0045]FIG. 19 is a plan view showing a magnetic impedance deviceaccording to a second embodiment of the present invention;

[0046]FIG. 20 is a cross-sectional view showing the device taken alongline XX-XX in FIG. 19;

[0047]FIG. 21 is a table showing the ratio of impedance change Δ Z/Zo indifferent devices, according to the second embodiment;

[0048]FIG. 22 is a graph showing a relationship between an externalmagnetic field Hext and impedance Z of the device according to thesecond embodiment;

[0049]FIG. 23 is a graph showing a relationship between an internalstress σ of a protection layer and a ratio of impedance change Δ Z/Zo ofthe devices according to the second embodiment;

[0050]FIG. 24 is a graph showing a relationship between an internalstress σ of a protection layer and a ratio of impedance change Δ Z/Zo ofthe devices according to the second embodiment;

[0051]FIG. 25 is a cross-sectional view showing a magnetic sensorapparatus according to a third embodiment of the present invention;

[0052]FIG. 26 is an enlarged plan view showing a magnetic impedancedevice of the apparatus according to the third embodiment;

[0053]FIG. 27 is a schematic diagram showing an electric circuit of theapparatus according to the third embodiment;

[0054]FIG. 28 is a cross-sectional view showing a magnetic sensorapparatus according to a fourth embodiment of the present invention;

[0055]FIG. 29 is a cross-sectional view showing a magnetic sensorapparatus according to a fifth embodiment of the present invention;

[0056]FIG. 30 is a cross-sectional view showing a magnetic sensorapparatus according to a sixth embodiment of the present invention;

[0057]FIG. 31 is a cross-sectional view showing part of a magneticsensor apparatus according to a seventh embodiment of the presentinvention;

[0058]FIG. 32 is a cross-sectional view showing a magnetic sensorapparatus according to an eighth embodiment of the present invention;

[0059]FIG. 33 is a cross-sectional view showing a magnetic sensorapparatus according to a ninth embodiment of the present invention;

[0060]FIG. 34 is a schematic cross-sectional view showing a rotationsensor apparatus according to a tenth embodiment of the presentinvention;

[0061]FIGS. 35A to 35C are schematic cross-sectional views showing partof the rotation sensor apparatus according to the tenth embodiment;

[0062]FIG. 36 is a schematic cross-sectional view showing anotherrotation sensor apparatus according to the tenth embodiment;

[0063]FIG. 37 is a schematic cross-sectional view showing a rotationsensor apparatus according to an eleventh embodiment of the presentinvention;

[0064]FIGS. 38A to 38C are schematic cross-sectional views showing arotation sensor apparatus according to a twelfth embodiment of thepresent invention;

[0065]FIG. 39 is a schematic cross-sectional view showing anotherrotation sensor apparatus according to the twelfth embodiment; and

[0066]FIGS. 40A and 40B are schematic cross-sectional views showing arotation sensor apparatus according to a thirteenth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIRST EMBODIMENT

[0067] The inventors examine a magnetic thin film made of Ni—Fe seriesalloy as a magnetic material composing a magnetic layer in a magneticimpedance device, which has high heat resistance so that sensitivity ofthe device is not decreased even when the device is processed with heattreatment above 400° C.

[0068] A magnetic impedance device according to a first embodimentutilizes magnetic impedance effect. The magnetic impedance effect isthat impedance of the device changes in accordance with an externalmagnetic field when the device is energized with an alternating current.The device includes a magnetic layer made of Ni—Fe series alloy film.Here, Ni—Fe series alloy film has high Currie temperature and is made ofpolycrystalline. Accordingly, magnetic property of the magnetic layermade of Ni—Fe series alloy film does not change after the heat treatmentabove 400° C. For example, sensor sensitivity of the device is notdecreased after the heat treatment. Therefore, the device has high heatresistance.

[0069] A magnetic impedance device 1 according to a first embodiment isshown FIGS. 1-3. As shown in FIGS. 1 and 2, the device 1 includes asubstrate 22, an insulation layer 24, a magnetic layer 26, and a pair ofelectrode pads 28 a, 28 b. The electrode pads 28 a, 28 b connect to analternating current supply 30. The alternating current supply 30 cancontrol a frequency of alternating current outputting from the supply30. In FIG. 1, an external magnetic field Hext is applied to the device1, and the alternating current outputted from the supply 30 also flowsthrough the device 1. An energization direction of the alternatingcurrent outputted from the supply 30 is parallel to the externalmagnetic field Hext.

[0070] The substrate 22 can be made of any material as long as theinsulation layer 24, the magnetic layer 26 and the like can be formedthereon. For example, the substrate is made of silicon wafer, glass,metal, and so on. In a case where the substrate 22 is made of conductingmaterial or semiconducting material such as metal or silicon, it ispreferred that the insulation layer 24 is disposed between the substrate22 and the magnetic layer 26 so that the magnetic layer 26 is insulatedfrom the substrate 22 electrically. In a case where the substrate 22 ismade of insulation material such as glass, the magnetic layer 26 can beformed on the substrate 22 directly without the insulation layer 24.Further, other material such as a conducting layer other than theinsulation layer 24 may be formed between the substrate 22 and themagnetic layer 26 in some case. Preferably, surface roughness of thesubstrate 22 is lower than 1 μm. In this case, concavity and convexityof the surface of the substrate 22 is small, and the magnetic layer 26is disposed on the substrate 22 directly or disposed on the substrate 22through the insulation layer 24 and the like, so that the magnetic layer26 can be magnetized easily. Specifically, the magnetic layer 26 has anexcellent soft magnetic property. Further, the insulation layer 24 canbe made of any insulation material as long as the insulation layer 24insulates between the substrate 22 and the magnetic layer 26. Forexample, the insulation layer 24 is made of oxide silicon, nitridesilicon, and the like.

[0071] The magnetic layer 26 is formed on the insulation layer 24. Themagnetic layer 26 is made of Ni—Fe series alloy film, which is a thinfilm and made of ferromagnetic material having a soft magnetic property.The Ni—Fe series alloy film is made of Ni and Fe only, i.e., Ni—Fealloy. However, the magnetic layer 26 can be made of Fe-Co alloy and thelike. Preferably, composition of Ni—Fe series alloy composing themagnetic layer 26 is 65-90 wt % of Ni and/or 15-35 wt % of Fe. In a casewhere the Ni—Fe series alloy is made of Ni and Fe only, it is preferredthat the composition is 65-90 wt % of Ni and/or 15-35 wt % of Fe. Inthis case, the sensor sensitivity is improved. More preferably,composition of Ni—Fe series alloy composing the magnetic layer 26 is77-85 wt % of Ni and/or 15-23 wt % of Fe. In a case where the Ni—Feseries alloy is made of Ni and Fe only, it is preferred that thecomposition is 77-85 wt % of Ni and/or 15-23 wt % of Fe. In the abovecases, the temperature dependence of magnetic permeability of themagnetic layer 26 becomes small, so that the magnetic impedance device 1has high sensor sensitivity and low temperature dependence of thesensitivity.

[0072] As shown in FIG. 3, the cross-section of the magnetic layer 26has a square shape, the cross-section being perpendicular to theenergization direction. The cross-section of the magnetic layer 26 has alatitudinal side 26 a and a longitudinal side 26 b. An angle θ betweenthe latitudinal side 26 a and the longitudinal side 26 b is preferablyin a range between 60° and 120°. In this case, wedge-shaped magneticdomain is prevented from generating. Therefore, a hysteresis loop in themagnetic impedance characteristic of the magnetic layer 26 is alsoprevented from generating. More preferably, the angle θ is in a rangebetween 85° and 95°.

[0073] Grain size of a single crystalline particle of the Ni—Fe seriesalloy composing the magnetic layer 26 is preferably in a range between 1nm and 1 μm. If the grain size is smaller than 1 nm, the grain sizebecomes larger when the device is performed with heat treatment.Therefore, the soft magnetic property is easily deteriorated. If thegrain size is larger than 1 μm, it is difficult to magnetize themagnetic layer 26 so as to have the soft magnetic property. Moreover, itis preferred that the magnetic layer 26 has an axis of easymagnetization, which is almost perpendicular to or parallel to theenergization direction of the alternating current from the alternatingcurrent supply 30. In this case, the detection sensitivity for detectingthe external magnetic field is improved. Further, it is preferred thatthe magnetic properties of the magnetic layer 26 are such that thecoercive force is lower than 10Oe and the relative magnetic permeabilityis higher than 500.

[0074] As shown in FIG. 1 and 2, the magnetic layer 26 has a length L1in the energization direction of the alternating current, a width L2perpendicular to the energization direction, and a thickness L3 of themagnetic layer 26. Assuming that a ratio between the length L1 and thewidth L2 is defined as α, i.e., α=L1/L2, and a ratio between the widthL2 and the thickness L3 is defined as β, i.e., β=L2/L3, the ratio α a isequal to or larger than 10 and the ratio β is in a range between 1 and50 (i.e., α≧10 and 1 ≦β≦50). Further, the thickness L3 is equal to orlarger than 5 μm. In this case, the magnetic impedance device has highsensor sensitivity. That is because the magnetic domain of the magneticlayer 26 can be controlled accurately so that the magnetic permeabilityof the magnetic layer 26 is largely changed in accordance with theexternal magnetic field in a case where the magnetic layer 26 has theabove construction.

[0075] More preferably, when the ration α is equal to or larger than 50,the sensor sensitivity is much improved. Further, when the ratio β is ina range between 1 and 30, the sensor sensitivity is much improved.Specifically, the ratio β is in a range between 1 and 5, the sensitivityis further improved. The above reasons are described later.

[0076] The electrode pads 28 a, 28 b are formed on the insulation layer24. Each electrode pad 28 a, 28 b covers one end or the other end of themagnetic layer 26 in the longitudinal direction. The electrode pad 18 a,28 b can be made of any material as long as the material works as anelectrode. For example, the material is aluminum, copper and theiralloy. It is preferred that the specific resistance of the electrode pad28 a, 28 b is equal to or lower than 10 μΩ·cm.

[0077] Next, the manufacturing method of the magnetic impedance device 1is describes as follows. At first, as shown in FIGS. 4A to 4C, thesubstrate 22 is prepared. Then, the insulation layer 24 is formed on thesubstrate 22. When the substrate 22 is made of silicon, the surface ofthe silicon substrate 22 is oxidized with using thermal oxidation methodso that the insulation layer 24 made of silicon oxides is formed.Further, the insulation layer 24 can be formed with using chemical vapordeposition method, sputtering method, or the like, and is made ofsilicon oxides, silicon nitrides. There is no limitation of thedeposition method for forming the insulation layer 24.

[0078] Next, the Ni—Fe series alloy film is formed on the insulationlayer 24. The Ni—Fe series alloy film can be formed with usingsputtering method, vapor deposition, or coating method. There is nolimitation of the deposition method for forming the Ni—Fe series alloy.The Ni—Fe series alloy film is patterned into a predetermined shape withusing photo etching method, so that the magnetic layer 26 is formed, asshown in FIG. 4C. In this case, preferably a single axial anisotropicmagnetic field is applied to the magnetic layer 26 in the energizationdirection of the alternating current, i.e., the longitudinal directionof the magnetic layer 26 during the deposition under magnetic filed orheat treatment under magnetic field, so that the magnetic layer 26 hasthe axis of easy magnetization along with the energization direction.

[0079] Next, a preliminary layer for an electrode is formed on both themagnetic layer 26 and the insulation layer 24. The preliminary layer canbe formed with using the sputtering method, vapor deposition, or coatingmethod. There is no limitation of the deposition method for forming thepreliminary layer. The preliminary layer is patterned into apredetermined shape with using photo etching method, so that theelectrode pads 28 a, 28 b are formed so as to cover both ends of themagnetic layer 26, as shown in FIGS. 1 and 2. Then, the electrodes 28 a,28 b is connected with bonding wires. Thus, the magnetic impedancedevice 1 is completed.

[0080] Specifically, the detailed manufacturing method is described asfollows. A magnetic impedance device S11 (that is shown in FIG. 8)according to this embodiment is manufactured. As shown in FIG. 4, thesilicon substrate 22 is prepared. The insulation layer 24 made ofsilicon oxides having thickness of 1 μm is formed on the substrate 22with using the thermal oxidation method.

[0081] Next, a Ni₈₁Fe₁₉ Alloy film having thickness of 2 μm is formed onthe insulation layer 24 with using the sputtering method under magneticfield. The Ni₈₁Fe₁₉ Alloy film is patterned into a predetermined shapewith using the photo etching method, so that the magnetic layer 26 isformed. Specifically, the magnetic layer 26 has a length of 2 mm and awidth of 10 μm . At this time, the single axial anisotropic magneticfield is applied to the magnetic layer 26 in the energization directionof the alternating current, i.e., the longitudinal direction of themagnetic layer 26 during the deposition of sputtering under magneticfiled, so that the magnetic layer 26 has the axis of easy magnetizationalong with the energization direction.

[0082] Next, an aluminum layer having thickness of 1 μm is formed onboth the insulation layer 24 and the magnetic layer 26. The aluminumlayer is patterned into a predetermined shape with using the photoetching method so that the electrode pads 28 a, 28 b are formed so as tocover both ends of the magnetic layer 26, as shown in FIGS. 1 and 2.Specifically, the area of each electrode pad 28 a, 28 b disposed on theupper surface of the electrode pad 28 a, 28 b is a square of 200 μm×200μm . On the assumption that the device S11 is processed in semiconductorprocess, the device S11 is processed in vacuum under 400° C. during 30minutes. After that, each electrode pad 28 a, 28 b is connected with abonding wire. Thus, the device S11 is completed.

[0083] The device S11 is evaluated with using a coil and an impedanceanalyzer. Here, the coil provides an external magnetic field Hextapplied to the device S11, and the impedance analyzer detects a highfrequency impedance Z generated at both ends of the magnetic layer 26 ofthe device S11. The external magnetic field Hext is parallel to theenergization direction of the high frequency alternating currentgenerated from the alternating current supply 30. The external magneticfield Hext is corrected with a gauss meter disposed on the substrate 22.The impedance Z is measured in case of the frequency of the highfrequency current supply 30 at 100 MHz. The magnetic impedance propertyof the device S11 is evaluated with a ratio of impedance change^(ΔZ)/_(Zo). Here, Zo is impedance of the device S11 in a case where theexternal magnetic field Hext is zero. ΔZ is a difference betweenimpedance Z in a case where the external magnetic field Hext is 100Oeand the impedance Zo at zero, i.e., ΔZ=Z−Zo. The temperature dependenceof the magnetic impedance of the device S11 is measured at −40° C. and+85° C. in a temperature controlled chamber, so that a coefficient oftemperature dependence of magnetic impedance Δ Zo/Δ T at zero magneticfield and a coefficient of temperature dependence of sensor sensitivityΔ (Δ Z/Zo)/Δ T are calculated. The coefficient of temperature dependenceof magnetic impedance Δ Zo/Δ T at zero magnetic field is a coefficientof temperature dependence of the impedance Z in case of the externalmagnetic field at zero. The coefficient of temperature dependence ofsensor sensitivity Δ (Δ Z/Zo)/Δ T is a coefficient of temperaturedependence of the ratio of impedance change Δ Z/Zo.

[0084]FIG. 5 is a graph of magnetic impedance property of the device S11showing an impedance change in accordance with the external magneticfield Hext. In case of the device S11, the impedance of the device S11is reduced in accordance with increasing or decreasing the externalmagnetic field Hext. As shown in FIG. 5, the ration of impedance changeΔ Z/Zo, which corresponds to the sensor sensitivity, is about 30%.

[0085]FIG. 6 shows a graph showing a relationship between temperature Tand an impedance drift Δ Z/Z at zero magnetic field, i.e., Z−Zat25°C./Zat25° C., of the device S11. The coefficient of temperaturedependence of magnetic impedance Δ Zo/Δ T at zero magnetic field iscalculated to be 723 ppm/° C. from a slope of a line of the relationshipbetween temperature T and the impedance drift Δ Z/Z.

[0086]FIG. 7 shows a graph showing a relationship between temperature Tand a sensor sensitivity drift$\frac{\Delta \left( \frac{\Delta \quad Z}{Z} \right)}{\left( \frac{\Delta \quad Z}{Z} \right)},$

[0087] i.e., Δ (Z−Zat25° C./Zat25° C.)/(Z−Zat25° C./Zat25° C.) of thedevice S11. The coefficient of temperature dependence of sensorsensitivity Δ (Δ Z/Zo)/Δ T is calculated to be −443 ppm/° C. from aslope of a line of the relationship between temperature T and the sensorsensitivity drift Δ (Δ Z/Z)/(Δ Z/Z).

[0088] In general, it is required that both of the coefficient oftemperature dependence of sensor sensitivity Δ (Δ Z/Zo)/Δ T and thecoefficient of temperature dependence of magnetic impedance Δ Zo/Δ T atzero magnetic field are in a range between −1000 ppm° C. to +1000 ppm/°C. Thus, both of the coefficients Δ (Δ Z/Zo)/Δ T, Δ Zo/Δ T arepreferably in a range between −1000 ppm/° C. to +1000 ppm/° C. Here,when the Ni—Fe alloy film has a composition of 77-85 wt % of Ni and/or15-23 wt % of Fe, this requirement of the coefficients Δ (Δ Z/Zo)/Δ T, ΔZo/Δ T are satisfied.

[0089] Both of the coefficients Δ (Δ Z/Zo)/Δ T, Δ Zo/Δ T of variousdevices S11-S18 are measured. As shown in FIG. 8, a device S12 has adifferent thickness of the magnetic layer 26, which is different fromthat of the device S11. Each device S13-S16 has the same construction asthe device S11, and different composition of Ni and Fe, which isdifferent from that of the device S11. Each device S17, S18 has the sameconstruction as the device S11, and has a various magnetic layer 26 madeof different materials, which is different from those of the device S11,specifically, the magnetic layer 26 of the device S17, S18 is made ofamorphous alloy.

[0090] As shown in FIG. 8, each device S11-S14 has a high sensorsensitivity, i.e., high ratio of impedance change Δ Z/Zo that is higherthan 20%, and low coefficients Δ (Δ Z/Zo)/Δ T, Δ Zo/Δ T, i.e., lowcoefficients of temperature dependence of sensor sensitivity Δ (ΔZ/Zo)/Δ T and of magnetic impedance Δ Zo/Δ T at zero magnetic field thatare in a range between −1000 ppm/° C. and +1000 ppm/° C. On the otherhand, the devices S15, S16 have the high sensor sensitivity that ishigher than 20%, and the high coefficients Δ (Δ Z/Zo)/Δ T, Δ Zo/Δ T thatare disposed out of range between −1000 ppm/° C. and +1000 ppm/° C. Thatis because the devices S11-S14 have the magnetic layer 26 made of theNi—Fe alloy film having a composition, which is disposed in a certainrange of the low temperature dependence of the relative magneticpermeability of the magnetic layer 26. However, the devices S15, S16have the magnetic layer 26 made of the Ni—Fe alloy film having acomposition, which is disposed in a certain range of the hightemperature dependence of the relative magnetic permeability of themagnetic layer 26.

[0091] Further, the devices S17, S18 have much small sensor sensitivity,which is much smaller than that of the devices S11-S16. That is becausethe devices S17, S18 have the magnetic layer 26 made of amorphous alloy,so that the magnetic layer 26 is crystallized in the heat treatmentprocess performed at 400° C. Therefore, the soft magnetic property ofthe magnetic layer 26 is almost disappeared. The soft magnetic propertyprovides the change of magnetic permeability in accordance with theexternal magnetic field.

[0092]FIG. 9 shows the ratio of impedance change Δ Z/Zo of variousdevices S21-S25, each of which has the magnetic layer 26 made of thesame composition of Ni and Fe as that of the device S11 (i.e.,Ni₈₁Fe₁₉). Each device S21-S25 has the magnetic layer 26 having athickness L3 of 2 μm, a width L2 of 10 μm, and a different length L1.FIG. 9 also shows the ratio α (i.e., α=L1/L2) and the ratio β (i.e.,β=L2/L3). FIG. 10 is a graph showing a relationship between the lengthL1 and the ratio of impedance change Δ Z/Zo of the various devicesS21-S25.

[0093] As shown in FIGS. 9 and 10, as the length L1 of the magneticlayer 26 becomes longer, the ratio of impedance change Δ Z/Zo becomeslarge. In the above devices S21-S25, the ratio β is 5. When the ratio αis equal to or larger than 10, i.e., the length L1 is equal to or longerthan 100 μm, the ratio of impedance change Δ Z/Zo is larger than 10%.Further, when the ratio α is equal to or larger than 50, i.e., thelength L1 is equal to or longer than 500 μm, the ratio of impedancechange Δ Z/Zo is larger than 20%. Furthermore, when the ratio α is equalto or larger than 200, i.e., the length L1 is equal to or longer than2000 μm, the ratio of impedance change Δ Z/Zo is larger than 30%. Here,it is preferred that the ratio of impedance change Δ Z/Zo becomeslarger.

[0094]FIG. 11 shows the ratio of impedance change Δ Z/Zo of variousdevices S31-S35, each of which has the magnetic layer 26 made of thesame composition of Ni and Fe as that of the device S11 (i.e.,Ni₈₁Fe₁₉). Each device S31-S35 has the magnetic layer 26 having athickness L3 of 2 μm, a length L1 of 2000 μm, and a different width L2.FIG. 11 also shows the ratio α (i.e., α=L1/L2) and the ratio β (i.e.,β=L2/L3). FIG. 12 is a graph showing a relationship between the width L2and the ratio of impedance change Δ Z/Zo of the various devices S31-S35.

[0095] As shown in FIGS. 11 and 12, in a case where the width L2 islonger than 10 μm, as the width L2 of the magnetic layer 26 becomeslonger, the ratio of impedance change Δ Z/Zo becomes small. In a casewhere the width L2 is shorter than 10 μm, as the width L2 of themagnetic layer 26 becomes shorter, the ratio of impedance change Δ Z/Zobecomes small rapidly. When the ratio α is in a range between 20 and 400and the ratio β is in a range between 1 and 5, i.e.,. the width L2 is ina range between 5 μm and 100 μm, the ratio of impedance change Δ Z/Zo islarger than 10%. Further, when the ratio α is in a range between 33.3and 333.3 and the ratio β is in a range between 1.2 and 30, i.e., thewidth L2 is in a range between 6 μm and 60 μm, the ratio of impedancechange Δ Z/Zo is larger than 20%. Furthermore, when the ratio α is in arange between 166.7 and 250 and the ratio β is in a range between 1.6and 2.4, i.e., the width L2 is in a range between 8 μm and 12 μm, theratio of impedance change Δ Z/Zo is larger than 30%. Here, it ispreferred that the ratio of impedance change Δ Z/Zo becomes larger.

[0096]FIG. 13 shows the ratio of impedance change Δ Z/Zo of variousdevices S41-S46, each of which has the magnetic layer 26 made of thesame composition of Ni and Fe as that of the device S11 (i.e.,Ni₈₁Fe₁₉). Each device S41-S46 has the magnetic layer 26 having a widthL2 of 10 μm, a length L1 of 2000 μm, and a different thickness L3. FIG.13 also shows the ratio α (i.e., α=L1/L2) and the ratio β (i.e.,β=L2/L3). FIG. 14 is a graph showing a relationship between thethickness L3 and the ratio of impedance change Δ Z/Zo of the variousdevices S41-S46.

[0097] As shown in FIGS. 13 and 14, as the thickness L3 of the magneticlayer 26 becomes thicker, the ratio of impedance change Δ Z/Zo becomeslarge. Here, the ratio α is 200. When the ratio β is equal to or smallerthan 33, i.e., the thickness L3 is equal to or larger than 0.3 μm, theratio of impedance change Δ Z/Zo is larger than 10%. Further, when theratio β is equal to or smaller than 14, i.e., the thickness L3 is equalto or larger than 0.7 μm, the ratio of impedance change Δ Z/Zo is largerthan 20%. Furthermore, when the ratio β is equal to or smaller than 5,i.e., the thickness L3 is equal to or larger than 2 μm, the ratio ofimpedance change Δ Z/Zo is larger than 30%.

[0098] In the above devices S11-S18, S21-S25, S31-S35, S41-S46 shown inFIGS. 8 to 14, it is preferred that the length L1, the width 12 and thethickness L3 have the following values.

[0099] Preferably, referring to the devices S22, S23, when the length L1is equal to or longer than 200 μm, the width L2 is in a range between 7μm and 20 μm, and the thickness L3 is equal to or larger than 2 μm,i.e., the ratio α is in a range between 10 and 28.6 and the ratio β isin a range between 3.5 and 10, the ratio of impedance change Δ Z/Zo isequal to or larger than 10%. Preferably, referring to the devices S31,S35, when the length L1 is equal to or longer than 2000 μm, the width L2is in a range between 5 μm and 50 μm, and the thickness L3 is equal toor larger than 2 μm, i.e., the ratio α is in a range between 40 and 400and the ratio β is in a range between 2.5 and 25, the ratio of impedancechange Δ Z/Zo is equal to or larger than 10%. Preferably, referring tothe devices S41, S42, when the length L1 is equal to or longer than 2000μm, the width L2 is in a range between 7 μm and 15 μm, and the thicknessL3 is equal to or larger than 0.3 μm, i.e., the ratio α is in a rangebetween 133.3 and 258.7 and the ratio β is in a range between 23.3 and50, the ratio of impedance change Δ Z/Zo is equal to or larger than 10%.

[0100] More preferably, referring to the devices S23, S24, S34, when thelength L1 is equal to or longer than 1000 μm, the width L2 is in a rangebetween 7 μm and 50 μm, and the thickness L3 is equal to or larger than2 μm, i.e., the ratio α is in a range between 20 and 142.9 and the ratioβ is in a range between 3.5 and 10, the ratio of impedance change Δ Z/Zois equal to or larger than 20%. In this case, it is much preferred thatthe width L2 is in a range between 7 μm and 20 μm. Preferably, referringto the device S43, when the length L1 is equal to or longer than 2000μm, the width L2 is in a range between 7 μm and 20 μm, and the thicknessL3 is equal to or larger than 0.5 μm, i.e., the ratio α is in a rangebetween 100 and 285.7 and the ratio β is in a range between 14 and 40,the ratio of impedance change Δ Z/Zo is equal to or larger than 20%.

[0101] Much more preferably, referring to the devices S25, S32, S45,when the length L1 is equal to or longer than 2000 μm, the width L2 isin a range between 7 μm and 20 μm, and the thickness L3 is equal to orlarger than 2 μm, i.e., the ratio α is in a range between 100 and 285.7and the ratio β is in a range between 3.5 and 10, the ratio of impedancechange Δ Z/Zo is equal to or larger than 30%.

[0102]FIG. 15 shows the ratio of impedance change Δ Z/Zo of variousdevices S51-S56, each of which has the magnetic layer 26 made of thesame composition of Ni and Fe as that of the device S11 (i.e.,Ni₈₁Fe₁₉). Each device S51-S56 has the magnetic layer 26 having a lengthL1 of 2000 μm a width L2 of 10 μm, a thickness L3 of 2 μm, and adifferent grain size. Here, each device has a surface roughness of thesubstrate 22 of 2 nm. FIG. 16 is a graph showing a relationship betweenthe grain size and the ratio of impedance change Δ Z/Zo of the variousdevices S51-S56.

[0103] As shown in FIGS. 15 and 16, as the grain size of the magneticlayer 26 becomes smaller, the ratio of impedance change Δ Z/Zo becomeslarge. When the grain size is equal to or smaller than 1100 nm, theratio of impedance change Δ Z/Zo is larger than 10%. Further, when thegrain size is equal to or smaller than 350 nm, the ratio of impedancechange Δ Z/Zo is larger than 20%. Furthermore, when the grain size isequal to or smaller than 10 nm, the ratio of impedance change Δ Z/Zo islarger than 30%.

[0104]FIG. 17 shows the ratio of impedance change Δ Z/Zo of variousdevices S61-S66, each of which has the magnetic layer 26 made of thesame composition of Ni and Fe as that of the device S11 (i.e.,Ni₈₁Fe₁₉). Each device S61-S66 has the magnetic layer 26 having a lengthL1 of 2000 μm a width L2 of 10 μm, a thickness L3 of 2 μm, and a grainsize of 10 nm. Each device has a different surface roughness of thesubstrate 22. FIG. 18 is a graph showing a relationship between thesurface roughness and the ratio of impedance change Δ Z/Zo of thevarious devices S61-S66.

[0105] As shown in FIGS. 17 and 18, as the surface roughness of thesubstrate 22 becomes smaller, the ratio of impedance change Δ Z/Zobecomes large. When the surface roughness is equal to or smaller than1300 nm, the ratio of impedance change Δ Z/Zo is larger than 10%.Further, when the surface roughness is equal to or smaller than 400 nm,the ratio of impedance change Δ Z/Zo is larger than 20%. Furthermore,when the surface roughness is equal to or smaller than 50 nm, the ratioof impedance change Δ Z/Zo is larger than 30%.

[0106] In the above devices having a certain construction, the sensorsensitivity is not decreased even when the device is processed with heattreatment. Thus, the device according to the first embodiment has highheat resistance. Further, the device has high sensor sensitivity.

SECOND EMBODIMENT

[0107] A magnetic impedance device 2 according to a second embodiment ofthe present invention includes the magnetic layer 26 and a protectionlayer 32, as shown in FIG. 19. The protection layer 32 covers themagnetic layer 26, and is made of electrically insulation material.

[0108] In general, a magnetic impedance device includes a magnetic layerhaving zero magneto-striction or low magneto-striction. This is becausethe magnetic layer having low magneto-striction is prevented fromchanging the magnetic properties generated by a striction of themagnetic layer, for example, from reducing the sensor sensitivity or thedetection accuracy. However, the inventors obtain the followingexperimental results. In the device having a protection layer forcovering the magnetic layer, an internal stress σ in the protectionlayer affects the magnetic properties of the magnetic layer, so that thesensor sensitivity is reduced. Further, there is a different influenceof the internal stress σ affecting the magnetic properties of themagnetic layer between a case where the internal stress σ of theprotection layer is a compression stress and a case where the internalstress σ is a tensile stress.

[0109] Considering the above experimental result, the device 2 accordingto the second embodiment includes the substrate 22, the insulation layer24, the magnetic layer 26, a pair of electrode pads 28 a, 28 b and theprotection layer 32. The external magnetic field Hext is applied to thedevice 2 along with the energization direction of the alternatingcurrent.

[0110] Although the magnetic layer id made of NI-Fe series alloy film,the magnetic layer 26 can be formed of linear shaped or thin film typeamorphous alloy such as Co—Nb—Zr alloy, Co—Si—B alloy, and the like.There is no limitation of the shape of the magnetic layer 26.

[0111] The protection layer 32 covers the surface of the magnetic layer26 and the surface of the insulation layer 24. The electrode pads 28 a,28 b are not covered with the protection layer 32, so that the electrodepads 28 a, 28 b are exposed from the protection layer 32. The protectionlayer 32 is made of non-magnetic material having electrically insulationproperty. Preferably, the protection layer 32 is made of, for example,silicon nitrides, aluminum nitrides, silicon oxides, phosphorizedsilicon oxides, and boron-doped silicon oxides. The protection layer 32made of these materials prevents from oxidizing in a case where themagnetic layer 26 is made of easily oxidized material such as Ni and/orFe, or prevents from crystallizing by heat treatment in a case where themagnetic layer 26 is made of amorphous alloy. Further, these materialsare usually used in a general semiconductor process, so that the device2 can be manufactured with using a general semiconductor process.Further, it is preferred that the protection layer 32 is formed ofcomposite material having a plurality of insulation materials or has alaminated structure. In this case, by a combination of a plurality ofinsulation materials, the internal stress σ of the protection layer 32can be reduced. Preferably, a thickness L11 of the protection layer 32is in a range between 0.2 μm and 5 μm. In this case, the protectionlayer 32 can protect the magnetic layer 26 sufficiently. Further, theprotection layer 32 is prevented from removing from the magnetic layer26 caused by the internal stress σ of the protection layer 32. Morepreferably, the thickness of the protection layer 32 is in a rangebetween 0.5 μm and 2 μm. In this case, the protection layer 32 protectsthe magnetic layer 26 much sufficiently. The above reasons are describedlater.

[0112] When the internal stress σ of the protection layer 32 is acompression stress, it is preferred that a magnitude of the compressionstress is lower than 500 MPa. When the internal stress σ of theprotection layer 32 is a tensile stress, it is preferred that themagnitude of the tensile stress is lower than 100 MPa. In this case, thesensor sensitivity of the device 2 is prevented from reducing caused bya deterioration of soft magnetic property of the magnetic layer 26 bythe internal stress σ of the protection layer 32. Further, theprotection layer 32 is prevented from removing from the magnetic layer26 caused by the internal stress σ of the protection layer 32. When theinternal stress σ0 of the protection layer 32 is a compression stress,more preferably the magnitude of the compression stress is lower than200 MPa. When the internal stress σ of the protection layer 32 is atensile stress, more preferably the magnitude of the tensile stress islower than 50 MPa. Preferably, the protection layer 32 has an insulationresistance, which is equal to or larger than 10 MΩ. The above reasonsare described later.

[0113] When the magnetic layer 26 is made of, for example, amorphousalloy, the amorphous alloy may be crystallized in a semiconductorprocess under high temperature higher than 400° C., so that the magneticproperty is changed, i.e., the sensor sensitivity is reduced. Therefore,when the magnetic layer 26 is made of a certain material such asamorphous material, which is easily affected by temperature, it ispreferred that the protection layer 32 is made of a material such asSiO₂, phospho-silicate glass (i.e., PSG), boro-silicate glass (i.e.,BSG) and boro-phospho-silicate glass (i.e., BPSG), which has low heatconductivity.

[0114] When the magnetic layer 26 includes a material such as Ni and/orCo, which is easily oxidized, it is considered that the heat treatmentunder high temperature higher than 400° C. in a semiconductor process isperformed in vacuum so that the magnetic layer 26 can be prevented fromoxidizing. However, additional equipment to perform the heat treatmentin vacuum is required, so that the manufacturing cost is increased. Onthe other hand, in a case where the protection layer 32 is disposed onthe magnetic layer 26, the magnetic layer 26 is prevented from oxidizingeven when the heat treatment is performed in the presence of oxygen, forexample, in air. Thus, no additional equipment to perform the heattreatment in vacuum is necessitated. Further, comparing with increase ofthe manufacturing cost to prepare the additional equipment of the heattreatment in vacuum, manufacturing cost increase of an additionalprocess to form the protection layer 32 is much lower. Moreover, themagnetic layer 26 is prevented from oxidizing by the protection layer 32after being manufactured.

[0115] Next, the magnetic impedance device 2 according to the secondembodiment is manufactured as follows. At first, as shown in FIGS. 4A to4C, the substrate 22 is prepared. Then, the insulation layer 24 isformed on the substrate 22. When the substrate 22 is made of silicon,the surface of the silicon substrate 22 is oxidized with using thermaloxidation method so that the insulation layer 24 made of silicon oxidesis formed. Further, the insulation layer 24 can be formed with usingchemical vapor deposition method, sputtering method, or the like, and ismade of silicon oxides, silicon nitrides. There is no limitation of thedeposition method for forming the insulation layer 24.

[0116] Next, a ferromagnetic film having a soft magnetic property isformed on the insulation layer 24. The ferromagnetic film can be formedwith using sputtering method, vapor deposition, or coating method. Thereis no limitation of the deposition method for forming the ferromagneticfilm. The ferromagnetic film is patterned into a predetermined shapewith using photo etching method, so that the magnetic layer 26 isformed, as shown in FIG. 4C. In this case, preferably the single axialanisotropic magnetic field is applied to the magnetic layer 26 in theenergization direction of the alternating current, i.e., thelongitudinal direction of the magnetic layer 26 with using depositionunder magnetic filed or heat treatment under magnetic field, so that themagnetic layer 26 has the axis of easy magnetization.

[0117] Next, a preliminary layer for an electrode is formed on both themagnetic layer 26 and the insulation layer 24. The preliminary layer canbe formed with using the sputtering method, vapor deposition, or coatingmethod. There is no limitation of the deposition method for forming thepreliminary layer. The preliminary layer is patterned into apredetermined shape with using photo etching method, so that theelectrode pads 28 a, 28 b are formed so as to cover both ends of themagnetic layer 26, as shown in FIGS. 1 and 2.

[0118] Next, an insulation material layer is formed on the insulationlayer 24, the magnetic layer 26 and the electrode pads 28 a, 28 b. Theinsulation material layer can be formed with using the CVD method (thatincludes a plasma CVD method), the sputtering method and the like. Thereis no limitation of deposition method. This insulation material layer ispatterned into a predetermined shape with using reactive ion etchingmethod (i.e., RIE method) and the like, so that part of the insulationmaterial layer disposed on the electrode pads 28 a, 28 b is removed.Thus, the protection layer 32 shown in FIGS. 19 and 20 is formed. Then,the electrodes 28 a, 28 b is connected with bonding wires. Thus, themagnetic impedance device 2 is completed.

[0119] Specifically, the detailed manufacturing method is described asfollows. A magnetic impedance device S205 (that is shown in FIG. 21)according to this embodiment is manufactured. As shown in FIG. 4, thesilicon substrate 22 is prepared. The insulation layer 24 made ofsilicon oxides having thickness of 1 μm is formed on the substrate 22with using the thermal oxidation method.

[0120] Next, a Ni₈₁Fe₁₉ Alloy film having thickness of 2 μm is formed onthe insulation layer 24 with using the sputtering method under magneticfield. The Ni₈₁Fe₁₉ Alloy film is patterned into a predetermined shapewith using the photo etching method, so that the magnetic layer 26 isformed. Specifically, the magnetic layer 26 has a length of 2 mm and awidth of 10 μm . At this time, the single axial anisotropic magneticfield is applied to the magnetic layer 26 in the energization directionof the alternating current, i.e., the longitudinal direction of themagnetic layer 26 with using the sputtering method under magnetic filed,so that the magnetic layer 26 has the axis of easy magnetization.

[0121] Next, aluminum layer having thickness of 1 μm is formed on boththe insulation layer 24 and the magnetic layer 26. The aluminum layer ispatterned into a predetermined shape with using the photo etching methodso that the electrode pads 28 a, 28 b are formed so as to cover bothends of the magnetic layer 26, as shown in FIGS. 1 and 2. Specifically,the area of each electrode pad 28 a, 28 b disposed on the upper surfaceof the electrode pad 28 a, 28 b is a square of 200 μm×200 μm.

[0122] Next, a silicon nitride layer having thickness of 1 μm is formedon the insulation layer 24, the magnetic layer 26 and the electrode pads28 a, 28 b with using the plasma CVD method. The silicon nitride layeris patterned into a predetermined shape with using the RIE method andthe like so that part of the insulation material layer disposed on theelectrode pads 28 a, 28 b is removed. Thus, the protection layer 32 isformed. On the assumption that the device S205 is processed insemiconductor process, the device S205 is processed in argon (i.e., Ar)gas atmosphere under 450° C. during 30 minutes. After that, eachelectrode pad 28 a, 28 b is connected with a bonding wire. Thus, thedevice S205 is completed.

[0123] The device S205 is evaluated with using a coil and an impedanceanalyzer. Here, the coil provides an external magnetic field Hextapplied to the device S205, and the impedance analyzer detects a highfrequency impedance Z generated at both ends of the magnetic layer 26 ofthe device S205. The external magnetic field Hext is parallel to theenergization direction of the high frequency alternating currentgenerated from the alternating current supply 30. The external magneticfield Hext is corrected with a gauss meter disposed on the substrate 22.The impedance Z is measured in case of the frequency of the highfrequency current supply 30 at 100 MHz. The magnetic impedance propertyof the device S205 is evaluated with a ratio of impedance change^(ΔZ)/_(Zo). Here, Zo is impedance of the device S205 in a case wherethe external magnetic field Hext is zero. ΔZ is a difference betweenimpedance Z in a case where the external magnetic field Hext is 100 Oeand the impedance Zo at zero, i.e., ΔZ=Z−Zo. The above evaluation isperformed before and after heat treatment under 450° C. so as to confirma protection effect of the protection layer 32.

[0124]FIG. 22 is a graph of magnetic impedance property of the deviceS205 showing an impedance change in accordance with the externalmagnetic field Hext before the heat treatment. In case of the deviceS205, the impedance of the device S205 is reduced in accordance withincreasing or decreasing the external magnetic field Hext. As shown inFIG. 5, the ration of impedance change Δ Z/Zo, which corresponds to thesensor sensitivity, is about 30%.

[0125] Next, the device S205 is heated in Ar gas atmosphere under 450°C. during 30 minutes. Then, the device is evaluated with the abovemethod. In this case, the magnetic impedance property of the device S205has the same relationship between the external magnetic field and themagnetic impedance as that of the device S205 before heat treatmentshown in FIG. 22. This result shows that the protection layer 32 made ofsilicon nitride covers the magnetic layer 26 made of Ni—Fe alloy film sothat the Ni—Fe alloy film composing the magnetic layer 26 is notoxidized by the heat treatment. Therefore, the magnetic properties ofthe magnetic layer 26 do not change substantially. Further, as describedlater, although the protection layer 32 of the device S205 has acompression stress of −120 MPa, the internal stress σ of the compressionstress does not affect the magnetic properties of the magnetic layer 26substantially.

[0126] Both of ratios of impedance change Δ Z/Zo before and after heattreatment of various devices S201-S219 are measured. As shown in FIG.21, devices S201-209 has the protection layer 32 made of silicon nitrideand a different thickness of the protection layer 32 and/or a differentinternal stress σ, which are different from those of the device S205.Each device S210-S218 has the protection layer 32 made of differentmaterial and a different thickness of the protection layer 32 and/or adifferent internal stress σ, which are different from those of thedevice S205. A device S219 has no protection layer 32.

[0127] As shown in FIG. 21, in the devices S202-S209, S211-S218, thesensor sensitivity, i.e., the ratio of impedance change Δ Z/Zo does notchange substantially before and after heat treatment. However, in thedevices S201, S210, S219, the sensor sensitivity changes largely beforeand after heat treatment. Namely, the sensor sensitivity of the deviceS201, S210, S219 is much decreased after the heat treatment. That isbecause the device S219 has no protection layer 32, so that the softmagnetic property of the magnetic layer 26 disappears after the heattreatment since the Ni—Fe alloy film composing the magnetic layer 26 isoxidized by the heat treatment under 450° C. Although the device S201,S210 has the protection layer 32, the thickness of the protection layer32 is 0.1 μm, which is so thin that the protection layer 32 can notprotect the magnetic layer 26 made of Ni—Fe alloy film from oxidation.

[0128]FIG. 23 shows the ratio of impedance change Δ Z/Zo of variousdevices S204-S206, each of which has the protection layer 32 made ofsilicon nitride. The thickness of the protection layer 32 of the deviceS204-S206 is 1 μm, and the internal stress σ of the protection layer 32is different from each other. FIG. 23 also shows the ratio of impedancechange Δ Z/Zo before and after heat treatment. Here, in a case where theinternal stress σ is positive, the internal stress σ is the tensilestress. In a case where the internal stress σ is negative, the internalstress σ is the compression stress.

[0129]FIG. 24 shows the ratio of impedance change Δ Z/Zo of variousdevices S213-S216, each of which has the protection layer 32 made ofsilicon oxides. The thickness of the protection layer 32 of the deviceS213-S216 is 1 μm, and the internal stress σ of the protection layer 32is different from each other. FIG. 24 also shows the ratio of impedancechange Δ Z/Zo before and after heat treatment.

[0130] As shown in FIGS. 22 and 23, as the internal stress σ of theprotection layer 32 becomes larger, the ratio of impedance change Δ Z/Zois decreased. Namely, the sensor sensitivity is reduced. That is becausea stress is generated in the magnetic layer 26 by the influence of theinternal stress σ of the protection layer 32 when the internal stress σof the protection layer 32 becomes large. Therefore, the magneticproperties of the magnetic layer 26 are changed, specifically, acoercive force of the magnetic layer 26 becomes large, so that therelative magnetic permeability of the magnetic layer 26 is reduced.Thus, the sensor sensitivity is reduced.

[0131] Further, there is a difference between one case where theinternal stress σ of the protection layer 32 is the tensile stress andthe other case where the internal stress σ is the compression stress.Specifically, even though the magnitude of the stress is the same, theratio of impedance change is different between the tensile stress andthe compression stress. More specifically, when the magnitude of theinternal stress σ is the same, the reduction of the ratio of impedancechange in case of the tensile stress is smaller than that in case of thecompression stress.

[0132] As shown in FIGS. 23 and 24, in a case where the tensile stressis equal to or smaller than 100 MPa, the ratio of impedance changebecomes larger than 20%. Preferably, in a case where the tensile stressis equal to or smaller than 50 MPa, the ratio of impedance changebecomes larger than 25%. In a case where the compression stress is equalto or smaller than 500 MPa, the ratio of impedance change becomes largerthan 20%. Preferably, in a case where the compression stress is equal toor smaller than 200 MPa, the ratio of impedance change becomes largerthan 25%.

[0133] In the above devices having a certain construction of theprotection layer 32, the sensor sensitivity is not decreased even whenthe device is processed with heat treatment. Thus, the device accordingto the second embodiment has high heat resistance. Specifically, themagnetic layer 26 of the device is not substantially oxidized even whenthe device is annealed. Further, the device has high sensor sensitivity.

THIRD EMBODIMENT

[0134] A magnetic sensor apparatus 300 having a magnetic impedancedevice 301 according to a third embodiment of the present invention isshown in FIGS. 25-27. FIG. 27 shows a schematic diagram of the apparatus300. The apparatus 300 includes the magnetic impedance device 301, aresistance 312, an oscillator 313, and an amplifier 314. Here, theresistance 312, the oscillator 313 and the amplifier 314 work as aperiphery circuitry. The periphery circuitry may include a regulatorcircuit, and an interface circuit for communicating with a signalbetween the apparatus 300 and an external circuit. The device 301 ismade of, for example, Ni—Fe series alloy, and connects to the resistance312 in series. Here, the device 301 made of Ni—Fe series alloy has awide dynamic range of detection of the magnetic field with using themagnetic impedance effect. Although the device 301 according to thisembodiment is made of Ni—Fe alloy, the device 301 can be formed of othermaterials. The resistance 312 and the device 301 also connect to bothends of the oscillator 313 in series. The oscillator 313 works as adriving circuit for supplying a high frequency current to the device301, and both ends of the oscillator 313 provide output terminals. Theabove series circuit composing the resistance 312, the device 301 andthe oscillator 313 has a common contact point for connecting to an inputterminal of the amplifier 314. The amplifier 314 amplifies a detectionsignal and outputs the amplified signal. Therefore, the amplifier 314works as a detection circuit for detecting impedance change of thedevice 301.

[0135]FIG. 25 is a cross-section showing the apparatus 300. FIG. 26 isan enlarged plan view showing the device 301. The apparatus 300 isformed with using a semiconductor manufacturing method in bipolarprocess. However, the apparatus 300 can be formed with using anothersemiconductor process such as MOS process and BiCMOS process. Theapparatus 300 includes a NPN type transistor 315 composing part of theamplifier 314, and a sensing portion 302 composing the magneticimpedance device 301.

[0136] The transistor 315 and the device 301 are disposed on asemiconductor substrate 322 made of P type silicon. Further, theresistance 312, the oscillator 313 and the amplifier 314 are disposed onthe substrate 322 (not shown).

[0137] The bipolar process for forming the transistor 315 is awell-known process of the semiconductor manufacturing method. Thetransistor 315 is formed with using implant patterning method, implantdiffusion method, separation patterning method, separation diffusionmethod, and the like, so that a base, an emitter and a collector thetransistor 315 are formed with using patterning method, diffusion methodand the like. Here, the semiconductor substrate 322 has an N type regiondisposed under the device 301. The N type region is formed with usingthe separation diffusion method.

[0138] Next, an insulation layer 324 made of silicon dioxide is formedon the substrate 322 and is patterned into a predetermined shape. Then,a wiring layer 328 made of aluminum and the like is formed on thesubstrate 322. The wiring layer 328 is patterned into a predeterminedshape so that part of the wiring layer is etched and removed so as toform the device 301. At that time a top end 328 a of the wiring layer328 is patterned into a tapered shape. The top end 328 a of the wiringlayer 328 connects to the device 301.

[0139] Then, Ni—Fe alloy composing the device 301 is deposited on thesubstrate 322 with using sputtering method under magnetic field. Thethickness of the Ni—Fe alloy deposited on the substrate 322 is in arange between 1 μm and 5 μm . Since the top end 328 a of the wiringlayer 328 is formed to be a tapered shape, the device 301, i.e., theNi—Fe alloy film is limited from cutting caused by fault of stepcoverage.

[0140] Next, to improve the magnetic properties of the device 301, theapparatus 300 is annealed at about 300° C. in vacuum under magneticfield. At last, a protection layer 332 made of silicon nitride, silicondioxide and the like is formed on the substrate 322.

[0141] Thus, the apparatus 300 having the device 301, the resistance312, the oscillator 313, the amplifier 314, and other circuits areformed on the substrate 322. Therefore, the apparatus 300 is manufactureto be compact and minimized so that the manufacturing cost of theapparatus 300 becomes small. Further, the device 301 is formed of thinfilm so that the dimensions of the device 301, specifically thickness ofthe device 301, are smaller than that having an amorphous wire. Thus,the apparatus 300 is formed to be compact.

[0142] Further, since the top end 328 a of the wiring layer 328connecting to both ends of the device 301 is formed to be a taperedshape, the Ni—Fe alloy film composing the device 301 is limited fromcutting at around the top end 328 a of the wiring layer 328. That isbecause the step coverage of the Ni—Fe alloy film at the top end 328 ais improved when the Ni—Fe alloy film is deposited on the wiring layer328.

[0143] Thus, the sensor apparatus 300 having the magnetic impedancedevice 301 according to this embodiment has minimum size and is madewith low manufacturing cost.

FOURTH EMBODIMENT

[0144] A magnetic sensor apparatus 303 having a magnetic impedancedevice 301A according to a fourth embodiment of the present invention isshown in FIG. 28. Although the device 301A according to this embodimentis made of Ni—Fe alloy, the device 301A can be formed of othermaterials. The apparatus 303 includes a metallic film 351 made oftitanium (i.e., Ti) material. The metallic film 351 is disposed on aconnecting portion between the wiring layer 328 and a magnetic impedancedevice 301A. The metallic film 351 is formed on the substrate before thewiring layer 328 is formed. Thus, the metallic film 351 electricallyconnects the wiring layer 328 and the device 301A. Then, the protectionlayer 332 is formed on the substrate 322.

[0145] In the apparatus 303, since the metallic film 351 made of Timaterial connects both ends of the device 301A and the top ends of thewiring layer 328, the connection between the device 301A and the wiringlayer 328 becomes excellent ohmic contact.

[0146] Thus, the sensor apparatus 303 having the magnetic impedancedevice 301A according to this embodiment has minimum size and is madewith low manufacturing cost. Further, the reliability of the connectionis improved.

FIFTH EMBODIMENT

[0147] A magnetic sensor apparatus 304 having a magnetic impedancedevice 301B according to a fifth embodiment is shown in FIG. 29.Although the device 301B according to this embodiment is made of Ni—Fealloy, the device 301B can be formed of other materials. The apparatus304 includes an interlayer insulation film 352 made of silicon oxides,silicon nitrides and the like. The interlayer insulation film 352 isformed on the substrate 322 after the device 301B and the wiring layer328 are formed on the substrate 322. The interlayer insulation film 352has a through hole for connecting the device 301B and the wiring layer328. In the through hole, a metallic film 351 made of aluminum material,copper material, Al-Ti series alloy or the like is filled and depositedso that the metallic film 351 connects the wiring layer 328 and thedevice 301B. Then, the protection layer 332 is formed on the substrate322.

[0148] In the apparatus 304, the interlayer insulation film 352 isformed on the upper surfaces of both the device 301B and the wiringlayer 328, and the metallic film 351 connects both ends of the device301B and the top ends of the wiring layer 328. Since the electricalconnection is disposed on the upper surfaces, so that the connectionbetween the device 301B and the wiring layer 328 becomes excellent ohmiccontact.

[0149] Thus, the sensor apparatus 304 having the magnetic impedancedevice 301B according to this embodiment has minimum size and is madewith low manufacturing cost. Further, the reliability of the connectionis improved.

SIXTH EMBODIMENT

[0150] A magnetic sensor apparatus 305 having the magnetic impedancedevice 301 according to a sixth embodiment is shown in FIG. 30. Theapparatus 305 includes a barrier metal film 354 made of Ti material andthe like. The barrier metal film 354 is formed on the top ends 328 a ofthe wiring layer and its neighboring portion. Then, the device 301 andthe protection layer 332 are formed on the substrate 322.

[0151] In the apparatus 305, since the barrier metal film 354 isdisposed on the top ends 328 a of the wiring layer and its neighboringportion, the connection portion between the device 301 and the wiringlayer 328 has a tri-layer structure. Therefore, the tri-layer structureprovides excellent ohmic contact between the device 301 and the wiringlayer 328.

[0152] Thus, the sensor apparatus 305 having the magnetic impedancedevice 301 according to this embodiment has minimum size and is madewith low manufacturing cost. Further, the reliability of the connectionis improved.

SEVENTH EMBODIMENT

[0153] A magnetic sensor apparatus 306 having the magnetic impedancedevice 301 according to a seventh embodiment is shown in FIG. 31. Theapparatus 306 includes a stress relaxation layer 355 made of poly-imide.However, the stress relaxation layer 355 can be formed of other organicmaterials or inorganic materials with using thin film depositiontechniques. The stress relaxation layer 355 is formed on the insulationlayer 324 before the wiring layer 328 is formed. Namely, the insulationlayer 324 is formed on the substrate 322, and the stress relaxation film355 is formed on the surface of the insulation layer 324. After that,the wiring layer 328 is formed on the stress relaxation layer 355. Thethickness of the stress relaxation layer is determined in accordancewith the thickness of the device 301 disposed on the stress relaxationlayer 355. For example, the thickness of the stress relaxation layer 355is in a range between 1 μm and 10 μm.

[0154] Next, the Ni—Fe alloy film composing the device 301 is depositedwith using the sputtering method so that the thickness of the Ni—Fealloy film is in a range between 1 μm and 5 μm . Then, to improve themagnetic properties of the device 301, the apparatus 306 is annealed atabout 300° C. in vacuum under magnetic field. At last, the protectionlayer 332 made of silicon nitride, silicon dioxide and the like isformed on the substrate 322.

[0155] When the apparatus 306 is annealed, a stress is generated in thesubstrate 322 since coefficient of thermal expansion of the substrate322 is different from that of the device 301. Therefore, in some cases,the substrate 322 may be cracked.

[0156] Conventionally, to prevent from cracking, deposition conditionfor depositing a magnetic layer composing a magnetic impedance device ischanged, or a film quality of the magnetic layer is changed. However, itis not considered about the crack in the substrate 322.

[0157] In the apparatus 306, the stress relaxation layer 355 is disposedbetween the substrate 322 and the device 301, so that the stress beingapplied to the substrate 322 is absorbed to the stress relaxation layer355. Thus, the substrate 322 is limited from cracking. Further, sincethe stress relaxation layer 355 is made of poly-imide, which is anorganic material, the stress relaxation layer 355 is easily formed.

[0158] Thus, the sensor apparatus 306 having the magnetic impedancedevice 301 according to this embodiment has minimum size and is madewith low manufacturing cost. Further, the reliability of the apparatusconcerned with a mechanical strength is improved.

EIGHTH EMBODIMENT

[0159] A magnetic sensor apparatus 307 having the magnetic impedancedevice 301B according to an eighth embodiment is shown in FIG. 32. Theapparatus 307 includes the stress relaxation layer 355. When the throughhole for connecting the device 301B and the wiring layer 328 is formedin the interlayer insulation film 352, the through hole goes through thestress relaxation layer 355 disposed under the interlayer insulationfilm 352 so that the through hole reaches the wiring layer 328.

[0160] In the apparatus 307, the substrate 322 is limited from cracking.Further, the interlayer insulation film 352 is formed on the uppersurfaces of both the device 301B and the wiring layer 328, and themetallic film 351 connects both ends of the device 301B and the top endsof the wiring layer 328. Since the electrical connection is disposed onthe upper surfaces, so that the connection between the device 301B andthe wiring layer 328 becomes excellent ohmic contact.

[0161] Thus, the sensor apparatus 307 having the magnetic impedancedevice 301B according to this embodiment has minimum size and is madewith low manufacturing cost. Further, the reliability of the apparatusconcerned with a mechanical strength is improved. Furthermore, thereliability of the connection is improved.

NINTH EMBODIMENT

[0162] A magnetic sensor apparatus 308 having the magnetic impedancedevice 301 according to a ninth embodiment is shown in FIG. 33. Theapparatus 308 includes an oxidation protection film 356 made of siliconnitrides, silicon dioxide and the like. The oxidation protection film356 is formed on the surface of the device 301.

[0163] Here, the magnetic properties of the device 301 depend on thesurface of the device since the device 301 utilizes the skin effect ofmagnetic thin film. Therefore, if the surface of the device 301 isoxidized, the magnetic detection of the device 301 is reduced.

[0164] Therefore, the oxidation protection film 356 protects the surfaceof the device 301 so as not to be oxidized. Thus, the magneticproperties of the device 301 can be maintained to be excellent.

[0165] Thus, the sensor apparatus 308 having the magnetic impedancedevice 301 according to this embodiment has minimum size and is madewith low manufacturing cost. Further, the apparatus 308 has high heatresistance.

[0166] The oxidation protection film 356 can be formed on the device300, 301A, 301B of the apparatus 303-307 shown in FIGS. 28-32.

TENTH EMBODIMENT

[0167] A rotation sensor apparatus 400 having a magnetic sensor 401according to a tenth embodiment of the present invention is shown inFIG. 34. The rotation sensor apparatus 400 includes a rotation body 411as an object to be detected its rotation, a casing 412 for covering therotation body 411, and the magnetic sensor 401. The casing 412 separatesbetween the rotation body 411 and the magnetic sensor 401. The magneticsensor 401 is provided by, for example, the magnetic sensor apparatus 25shown in FIG. 25. Therefore, the magnetic sensor 401 includes a magneticimpedance sensor.

[0168] The rotation body 411 is made of a magnetic material or amaterial including the magnetic material, and is a gear having agearwheel shape. When the rotation body 411 rotates, a magnetic fieldaround the rotation body 411 changes repeatedly.

[0169] In a case where the rotation body 411 is made of magneticmaterial, the rotation body 411 is magnetized by a surrounding magneticfield. Therefore, the rotation body 411 works as a magnetized gear 411a, as shown in FIG. 35A. The magnetized gear 411 a attracts a permanentmagnet. In FIG. 35A, a pair of arrows shows magnetic field linesgenerated by the magnetized gear 411 a. When the magnetized gear 411 arotates, the magnetic field lines also rotate so that the intensity ofmagnetic field around the magnetized gear 411 a changes periodically.

[0170] In a case where the rotation body 411 is not magnetized, therotation body works as a non-magnetized gear 411 b. Even though thenon-magnetized gear 411 b is not magnetized, the intensity of magneticfield around the non-magnetized gear 411 b changes periodically. That isbecause the magnetic field lines of the geomagnetic filed changesperiodically by alternating appearance of a concavity and convexity ofperiphery of the gear 411 b when the non-magnetized gear 411 b rotates.As shown in FIGS. 35B and 35C, when the concavity of the gear 411 bfaces the magnetic sensor 401, the intensity of magnetic field aroundthe magnetic sensor 401 becomes weak. When the convexity of the gear 411b faces the magnetic sensor 401, the intensity of magnetic field aroundthe magnetic sensor 401 becomes strong. Thus, the intensity of magneticfield around the gear 411 b changes periodically.

[0171] Thus, the magnetic sensor 401 detects the periodic change of theintensity of magnetic field when the rotation body 411 rotates.Therefore, the rotation of the rotation body 411 can be detected by themagnetic sensor 401.

[0172] The magnetic sensor 401 is, for example, a magnetic sensorapparatus having a magnetic impedance device. The magnetic sensorapparatus includes a Ni—Fe series alloy film formed on a non-magneticsubstrate. As shown in FIG. 35, the Ni—Fe series alloy film of themagnetic sensor 401 has a predetermined pattern in such a manner that aplurality of linear shaped films is arranged at predetermined intervalsparallel to a magnetic field detection direction, and is repeatedlyconnected together so that they forms a switchback shape.

[0173] A high frequency alternating current is applied to both ends ofthe Ni—Fe series alloy film of the magnetic sensor 401, so that theimpedance between both ends is changed in accordance with the change ofthe external magnetic field. The impedance change is measured by anelectric circuit (not shown), and then the impedance change is convertedto an electric signal. The electric signal is outputted from themagnetic sensor 401. Thus, the signal, which corresponds to the rotationof the rotation body 411, is obtained.

[0174] The magnetic sensor 401 having the magnetic impedance device hashigh sensor sensitivity, which is much higher than that of aconventional magneto-resistance sensor or hall element sensor.Accordingly, even when the magnetic sensor 401 is disposed outside thecasing 412, the magnetic sensor 401 can detect the change of magneticfield generated by the rotation of the rotation body 411 disposed in thecasing 412 so that the magnetic sensor 401 detects the rotation of therotation body 411. Specifically, the magnetic sensor 401 detects theperiodic change of the intensity of magnetic field, which is generatedby the rotation of the rotation body 411 and leaks outside the casing412. Then, the magnetic sensor 401 converts the signal to the electricsignal. Here, the magnetic sensor 401 includes a driving circuit, asensing portion, a detection circuit, a regulator, and an input-outputcircuit (not shown).

[0175] The casing 412 works as a separation shield for separatingbetween the rotation body 411 and the magnetic sensor 401. The casing412 is made of aluminum. However, the casing 412 can be made of othernon-magnetic materials such as copper and brass. Further, the casing 412can be made of non-metallic non-magnetic materials such as resin andceramics. When the casing is made of non-magnetic material, which doesnot attract a permanent magnet, the periodic change of the intensity ofmagnetic field generated by the rotation of the rotation body 411 is notsubstantially disturbed by the casing 412. Therefore, even when themagnetic sensor 401 is disposed outside the casing 412, the magneticsensor 401 can detect the rotation of the rotation body 411 accurately.

[0176] Here, since the magnetic sensor 401 has high sensor sensitivity,the rotation sensor apparatus 400 has no bias magnet for applying anadditional magnetic field as a bias magnetic field.

[0177]FIG. 36 shows a rotation sensor apparatus 402 having a pair ofmagnetic sensors 401A, 401B. In the apparatus 402, two magnetic sensors401A, 401 b are arranged in parallel so as to separate by a half ofpitch of the rotation body 411, i.e., by a half pitch of gear. Theapparatus 402 detects a differential output generated from both magneticsensors 401A, 401B. This differential output cancels a constantcomponent of the geomagnetic field disposed in each magnetic sensor401A, 401B. Therefore, the apparatus 402 detects the periodic change ofmagnetic field much accurately. Namely, the apparatus 402 detects therotation much accurately.

[0178] In each apparatus 400, 402, the magnetic sensor 401, 401A, 401Bhaving high sensor sensitivity can detect the rotation of the rotationbody 411, 411 a, 411 b, even though the casing 412 as a separationshield is disposed between the magnetic sensor 401, 401A, 401B and therotation body 411, 411 a, 411 b. Therefore, the magnetic sensor 401,401A, 401B can be disposed outside the casing 412 without drilling anopening for mounting the magnetic sensor 401, 401A, 401B. Thus, theapparatus 400, 402 has high mounting performance for mounting themagnetic sensor 401, 401A, 401B on the casing 412 and high designfreedom of the casing 412.

[0179] The apparatus 400, 402 is suitably used for detecting a rotationof a cam of camshaft in an engine of an automotive vehicle or a gear ofa crankshaft in an engine of a vehicle. The apparatus 400, 402 candetect the rotation without opening a hole for detecting the rotation,i.e., without drilling in a wall of engine casing (e.g., an engineblock) of the vehicle. Accordingly, the apparatus 400, 402 has highmounting performance on the engine of the vehicle, so that designfreedom for mounting the apparatus on the engine, on which a lot ofparts are mounted, is improved.

[0180] Further, the apparatus 400, 402 can detect a rotation of a wheelof an automotive vehicle. For example, the magnetic sensor 401, 401A,401B detects the periodic change of the intensity of magnetic field inaccordance with the rotation of the wheel. Then, the apparatus 400, 402outputs the electric signal so that the apparatus 400, 402 detects therotation of the wheel. Here, the magnetic sensor 401, 401A, 401B ismounted on an engine hood of the vehicle or in a compartment of thevehicle.

ELEVENTH EMBODIMENT

[0181] A rotation sensor apparatus 403 having the magnetic sensor 401according to an eleventh embodiment of the present invention is shown inFIG. 37. The rotation sensor apparatus 403 includes a rotation body 411c, the casing 412 and the magnetic sensor 401. The rotation body 411 cincludes a cylindrical magnet. Each of N and S poles of the cylindricalmagnet is alternately disposed on a circumferential periphery of thecylindrical magnet.

[0182] As shown in FIG. 37, a center axis of the cylindrical magnetworks as a rotation axis, so that the rotation body 411 c works as amagnetic rotor having a pair of magnet poles disposed alternately on thecircumferential periphery of the rotor. Magnetic field lines generatedby the rotation body 411 c output from the rotation body 411 c, and aredisposed periodically. When the rotation body 411 c rotates, a periodicchange of the intensity of magnetic field is generated around therotation body 411 c. This periodic change is detected by the magneticsensor 401 disposed outside the casing 412, so that the apparatus 403can detect the rotation of the rotation body 411 c.

[0183] Although the apparatus 403 has a single magnetic sensor 401, theapparatus can have a pair of magnetic sensors. In this case, twomagnetic sensors are arranged in parallel to separate by a half of pitchof the rotation body 411 c. The apparatus detects a differential outputgenerated from both magnetic sensors. This differential output cancels aconstant component of the geomagnetic field disposed in each magneticsensor. Therefore, the apparatus detects the rotation much accurately.Specifically, in a case where the intensity of magnetization of therotation body 411 c is weak so that the periodic change of the intensityof magnetic field in accordance with the rotation of the rotation body411 c is small, the apparatus 403 having a pair of magnetic sensors caneffectively detect the rotation.

[0184] In the apparatus 403, the magnetic sensor 401 having high sensorsensitivity can detect the rotation of the rotation body 411 c, eventhough the casing 412 as a separation shield is disposed between themagnetic sensor 401 and the rotation body 411 c. Therefore, the magneticsensor 401 can be disposed outside the casing 412 without drilling anopening for mounting the magnetic sensor 401. Thus, the apparatus 403has high mounting performance for mounting the magnetic sensor 401 onthe casing 412 and high design freedom of the casing 412.

[0185] The apparatus 403 is suitably used for detecting a rotation of amagnetized rotor mounted on a rotation shaft of a wheel of an automotivevehicle. In this case, the apparatus 403 provides a wheel rotationsensor for anti lock break system (i.e., ABS) of the vehicle. In theABS, the magnetic sensor 401 is mounted on a wheel hub as a rotor casingwithout drilling a hole in the rotor casing. Accordingly, the apparatus403 can mount on the wheel hub, which is required to have a narrowmounting portion since the wheel and a suspension are nearly disposed.Thus, the apparatus 403 has high mounting performance to the wheel hub,so that design freedom for mounting the apparatus 403 on the wheel hubis improved.

[0186] Further, the apparatus 403 can detect a rotation of a wheel of anautomotive vehicle. In this case, the magnetic sensor 401 is mounted onan engine hood of the vehicle or in a compartment of the vehicle.

TWELFTH EMBODIMENT

[0187] Rotation sensor apparatuses 500, 501 having the magnetic sensor401 according to a twelfth embodiment of the present invention are shownin FIGS. 38A to 38C. Each rotation sensor apparatus 500, 501 includesthe magnetized gear 411 a or the non-magnetized gear 411 b as a rotationbody 411 as an object to be detected its rotation, the magnetic sensor401, a sensor casing 512 for covering the magnetic sensor 401. Thesensor casing 512 separates between the rotation body 411 and themagnetic sensor 401.

[0188] The sensor casing 512 covers the magnetic sensor 401, and is madeof magnetic material. The sensor casing 512 includes an opening 513disposed between the magnetic sensor 401 and the rotation body 411.Namely, the opening 513 faces the rotation body 411. In the apparatus500, 501, the magnetic sensor 401 having high sensor sensitivity issurrounded by the sensor casing 512 having high magnetic permeability.Accordingly, the sensor casing 512 partially shields a magnetic field sothat influence of disturbance of an external magnetic field around themagnetic sensor 401 is reduced. Namely, the apparatus 500, 501 has highresistance against the outside disturbance of magnetic field.

[0189] The periodic change of the intensity of magnetic field generatedby the rotation of the rotation body 411 is detected by the magneticsensor 401 through the opening 513 of the sensor casing 512. Thus, themagnetic sensor 401 can detect the rotation of the rotation body 411.Here, since the magnetic sensor 401 has high sensor sensitivity fordetecting magnetic field, the opening 513 of the sensor casing 512 canbe minimized as long as the magnetic sensor 401 detects the periodicchange of the intensity of magnetic field.

[0190] Thus, the apparatus 500, 501 has a simple construction in such amanner that the sensor casing 512 having a small opening 513 covers themagnetic sensor 401 so that the influence of disturbance of an externalmagnetic field around the magnetic sensor 401 is reduced. Therefore, themanufacturing cost of the apparatus 500, 501 is reduced.

[0191] The apparatus 500, 501 is suitably used for detecting a rotationof a cam of camshaft in an engine of an automotive vehicle or a gear ofa crankshaft in an engine of a vehicle. Here, there are many sources togenerate disturbance of the external magnetic field around the engine ofthe vehicle. Further, the disturbance of the external magnetic field hasa complicated structure. Even when the apparatus 500, 501 is disposed insuch a complicated disturbance, the influence of disturbance is reducedso that the apparatus 500, 501 detects the rotation accurately.

[0192] Although the rotation body 411 has a gearwheel shape and is madeof a magnetic material or a material including the magnetic material,the rotation body 411 can have another shape and be made of anothermaterial. As shown in FIG. 39, a rotation sensor apparatus 502 has therotation body 411 c. The rotation body 411 c includes a cylindricalmagnet. Each of N and S poles of the cylindrical magnet is alternatelydisposed on a circumferential periphery of the cylindrical magnet. Theapparatus 502 further includes the magnetic sensor 401 and the sensorcasing 512 having the opening 513. In the apparatus 502, the sensorcasing 512 partially shields a magnetic field so that influence ofdisturbance of an external magnetic field around the magnetic sensor 401is reduced. Further, the magnetic sensor 401 detects the periodic changeof the intensity of magnetic field generated by the rotation of therotation body 411 c through the opening 513 of the sensor casing 512.Thus, the magnetic sensor 401 can detect the rotation of the rotationbody 411 c.

[0193] Thus, the apparatus 502 has a simple construction in such amanner that the sensor casing 512 having the small opening 513 coversthe magnetic sensor 401 so that the influence of disturbance of anexternal magnetic field around the magnetic sensor 401 is reduced.Therefore, the manufacturing cost of the apparatus 502 is reduced.

[0194] The apparatus 502 is suitably used for detecting a rotation of amagnetized rotor mounted on a rotation shaft of a wheel of an automotivevehicle. In this case, the apparatus 502 provides a wheel rotationsensor for ABS of the vehicle. Here, there are many sources to generatedisturbance of the external magnetic field under a body of the vehicle.Further, the disturbance of the external magnetic field has acomplicated structure. Even when the apparatus 502 is disposed in such acomplicated disturbance, the influence of disturbance is reduced so thatthe apparatus 502 detects the rotation accurately.

THIRTEENTH EMBODIMENT

[0195] A rotation sensor apparatus 503 having the magnetic sensor 401according to a thirteenth embodiment of the present invention is shownin FIGS. 40A and 40B. The rotation sensor apparatus 503 includes therotation body 411 made of a magnetic material or a material includingthe magnetic material, the magnetic sensor 401, and a sensor casing 512a for covering the magnetic sensor 401. The sensor casing 512 a is madeof permanent magnet. Both ends of the sensor casing 512 a are opened,and the sensor casing 512 a has a cylindrical shape. One end of thesensor casing 512 a has an opening 513 a, which faces the rotation body411. The sidewall of the sensor casing 512 a is formed of the permanentmagnet. In the sensor casing 512 a, the magnetic sensor 401 is disposed.Specifically, the magnetic sensor 401 is disposed on the rotation bodyside, and does not protrude from the opening 513 a of the sensor casing512 a.

[0196] In the apparatus 503, the magnetic sensor 401 having high sensorsensitivity is surrounded by the sensor casing 512 a made of thepermanent magnet. The external magnetic field is prevented frominserting into the sensor casing 512 a except for the opening 513 abecause the sensor casing 512 a is made of the permanent magnet. Thus,the sensor casing 512 a works as a magnetic shield for shielding thedisturbance of the external magnetic field.

[0197] Further, the sensor casing 512 a works as not only a magneticshield but also a bias magnet for applying a bias magnetic field shownas arrows in FIGS. 40A and 40B. The one end of the sensor casing 512 a,at which the opening 513 a is disposed, provides one pole, and the otherend provides the other pole. Therefore, the maximum bias magnetic fieldis applied toward the rotation body 411. Part of the bias magnetic fieldpenetrates into a cavity of the sensor casing 512 a, so that part of thebias magnetic field reaches the magnetic sensor 401. When the rotationbody 411 rotates, the concavity and convexity disposed on acircumferential periphery of the rotation body 411 changes the magneticfield lines of the bias magnetic field periodically. Therefore, theperiodic change of the intensity of magnetic field in accordance withthe rotation of the rotation body 411 affects the bias magnetic fieldpenetrated in the cavity of the sensor casing 512 a. Thus, the magneticsensor 401 detects this periodic change of the intensity of magneticfield, so that the apparatus 503 detects the rotation of the rotationbody 411.

[0198] The periodic change of the intensity of magnetic field inaccordance with the rotation of the rotation body 411 can be enlarged bycontrolling the bias magnetic field of the permanent magnet composingthe sensor casing 512 a, even in a case where the rotation body 411 isnot magnetized so that no magnetic field is generated by the rotationbody 411. Therefore, the magnetic sensor 401 can detect the rotationaccurately.

[0199] With using the rotation sensor apparatus 503 having the sensorcasing 512 a made of the permanent magnet, detection accuracy fordetecting the rotation is improved. Here, when the opening 513 a becomessmall, the bias magnetic field is difficult to penetrate into the cavityof the sensor casing 512 a. However, the magnetic sensor 401 with themagnetic impedance device has high sensor sensitivity for detecting themagnetic field, so that the opening 513 a of the sensor casing 512 a canbe minimized as long as the magnetic sensor 401 detects the periodicchange of the intensity of magnetic field.

[0200] Thus, the apparatus 503 has a simple construction in such amanner that the sensor casing 512 a having the small opening 513 acovers the magnetic sensor 401 so that the influence of disturbance ofan external magnetic field around the magnetic sensor 401 is reduced.Therefore, the manufacturing cost of the apparatus 503 is reduced.

[0201] The apparatus 503 is suitably used for detecting a rotation of acam of camshaft in an engine of an automotive vehicle or a gear of acrankshaft in an engine of a vehicle.

[0202] Although the apparatus 503 includes the rotation body 411, theapparatus 503 can have another type of rotation body such as therotation body 411 c, of which N and S poles are disposed alternately ona circumferential periphery thereof. In this case, the sensor casing 512a is not required to work as a bias magnet. Therefore, the sensor casing512 a merely works as a magnetic shield. In this case, the apparatus 503provides a wheel rotation sensor for ABS of the vehicle.

[0203] Such changes and modifications are to be understood as beingwithin the scope of the present invention as defined by the appendedclaims.

What is claimed is:
 1. A magnetic sensor apparatus comprising: asemiconductor substrate; and a magnetic impedance device for detecting amagnetic field, wherein the magnetic impedance device is disposed on thesubstrate.
 2. The apparatus according to claim 1, further comprising: aperiphery circuit for processing an output signal outputted from themagnetic impedance device, wherein the periphery circuit is disposed onthe substrate.
 3. The apparatus according to claim 2, furthercomprising: a wiring layer made of aluminum material, wherein the wiringlayer connects to both ends of the magnetic impedance device, andwherein the wiring layer has a pair of ends, which is disposed on aconnection portion between the wiring layer and the magnetic impedancedevice.
 4. The apparatus according to claim 3, wherein each end of thewiring layer has a tapered shape.
 5. The apparatus according to claim 3,further comprising: a barrier metal film made of titanium material,wherein the wiring layer connects to both ends of the magnetic impedancedevice through the barrier metal film.
 6. The apparatus according toclaim 3, further comprising: a metallic film, wherein the wiring layerconnects to both ends of the magnetic impedance device through themetallic film.
 7. The apparatus according to claim 6, furthercomprising: an interlayer insulation film, wherein the interlayerinsulation film is disposed between the magnetic impedance device andthe metallic film.
 8. The apparatus according to claim 6, wherein themetallic film is made of titanium material.
 9. The apparatus accordingto claim 6, wherein the metallic film is made of aluminum material,copper material, mixture of aluminum and titanium materials, or mixtureof copper and titanium materials.
 10. The apparatus according to claim2, wherein the magnetic impedance device is made of Ni—Fe series alloy.11. The apparatus according to claim 2, further comprising: a stressrelaxation layer disposed between the substrate and the magneticimpedance device, wherein the stress relaxation layer reduces a stressgenerated in the substrate in a case where the apparatus is processed ina heat treatment.
 12. The apparatus according to claim 11, wherein thestress relaxation layer is made of poly-imide.
 13. The apparatusaccording to claim 2, further comprising: an oxidation protection filmdisposed on the magnetic impedance device.
 14. The apparatus accordingto claim 13, wherein the oxidation protection film is made of siliconoxides, silicon nitrides, or composite film of silicon oxides andsilicon nitrides.
 15. A method for manufacturing the magnetic sensorapparatus according to claim 1, the method comprising the steps of:forming a stress relaxation layer on the substrate; and forming themagnetic impedance device on the stress relaxation layer, wherein thestress relaxation layer reduces a stress generated in the substrate in acase where the apparatus is processed in a heat treatment.
 16. Themethod according to claim 15, wherein the stress relaxation layer ismade of poly-imide.
 17. The method according to claim 15, furthercomprising the steps of: forming an oxidation protection film on themagnetic impedance device.
 18. The method according to claim 17, whereinthe oxidation protection film is made of silicon oxides, siliconnitrides, or composite film of silicon oxides and silicon nitrides. 19.The apparatus according to claim 1, wherein the magnetic impedancedevice detects a magnetic field in such a manner that impedance of thedevice is changed in accordance with the magnetic filed when analternating current is applied to the device and the impedance ismeasured by an external electric circuit, wherein the magnetic impedancedevice includes a magnetic layer made of Ni—Fe series alloy film,wherein the magnetic layer has a length defined as L1 in an energizationdirection of the alternating current, a width defined as L2 in aperpendicular direction perpendicular to the energization direction, anda thickness of the magnetic layer defined as L3, wherein the ratio ofthe length and the width is defined as α, i.e., α=L1/L2, and the ratioof the width and the thickness is defined as β, i.e., β=L2/L3, whereinthe ratio α is equal to or larger than 10, and the ratio β is in a rangebetween 1 and 50, and wherein the thickness L3 is equal to or largerthan 5 μm.
 20. The apparatus according to claim 19, wherein the Ni—Feseries alloy film has a composition such that a content of Ni in theNi—Fe series alloy film is in a range between 65 wt % and 90 wt %,and/or a content of Fe in the Ni—Fe series alloy film is in a rangebetween 10 wt % and 35 wt %.
 21. The apparatus according to claim 19,wherein the magnetic layer has a square shaped cross-section, which isdisposed perpendicular to the energization direction of the alternatingcurrent applied to the magnetic layer, and wherein the square shapedcross-section has one side and the other side, an angle of which is in arange between 60° and 120°.
 22. The apparatus according to claim 19,wherein the Ni—Fe series alloy film has a plurality of grains,dimensions of which are in a range between 1 nm and 1 μm.
 23. Theapparatus according to claim 19, wherein the magnetic layer is disposedon the substrate with or without a buffer layer therebetween, andwherein the substrate has a surface roughness, which is equal to orsmaller than 1 μm.
 24. The apparatus according to claim 19, wherein themagnetic layer has an axis of easy magnetization, which is substantiallyparallel to or perpendicular to the energization direction of thealternating current.
 25. The apparatus according to claim 1, wherein themagnetic impedance device detects a magnetic field in such a manner thatimpedance of the device is changed in accordance with the magnetic filedwhen an alternating current is applied to the device and the impedanceis measured by an external electric circuit, wherein the magneticimpedance device includes a magnetic layer made of Ni—Fe series alloyfilm, wherein the magnetic layer has a length defined as L1 in anenergization direction of the alternating current, a width defined as L2in a perpendicular direction perpendicular to the energizationdirection, and a thickness of the magnetic layer defined as L3, andwherein the length L1 is equal to or larger than 100 μm, the width L2 isin a range between 5 μm and 100 μm, the thickness L3 is equal to orlarger than 0.3 μm.
 26. The apparatus according to claim 25, wherein theNi—Fe series alloy film has a composition such that a content of Ni inthe Ni—Fe series alloy film is in a range between 65 wt % and 90 wt %,and/or a content of Fe in the Ni—Fe series alloy film is in a rangebetween 10 wt % and 35 wt %, wherein the Ni—Fe series alloy film has aplurality of grains, dimensions of which are equal to or smaller than100 nm, and wherein the substrate has a surface roughness, which isequal to or smaller than 1300 nm.
 27. The apparatus according to claim19, further comprising: a protection layer for covering the magneticlayer, wherein the protection layer is made of electrically insulationmaterial.
 28. The apparatus according to claim 27, wherein theprotection layer has a compression stress as an internal stress, thecompression stress being equal to or smaller than 500 MPa.
 29. Theapparatus according to claim 27, wherein the protection layer has atensile stress as an internal stress, the tensile stress being equal toor smaller than 100 MPa.
 30. The apparatus according to claim 27,wherein the protection layer has a thickness in a range between 0.2 μmand 5 μm.
 31. The apparatus according to claim 27, wherein theprotection layer is made of at least one of materials selected from thegroup consisting of silicon nitrides, aluminum nitrides, silicon oxides,phosphorized silicon oxides, and boron-doped silicon oxides.
 32. Theapparatus according to claim 27, wherein the protection layer is made ofa composite material having a plurality of insulation materials.
 33. Theapparatus according to claim 27, wherein the protection layer has alaminated structure.
 34. A rotation sensor apparatus comprising: arotation body for providing a periodic change of intensity of magneticfield disposed around the rotation body in accordance with rotation ofthe rotation body; a magnetic sensor having a magnetic impedance devicefor detecting the periodic change of the intensity of magnetic field soas to detect the rotation of the rotation body; and a separation shieldfor separating between the rotation body and the magnetic sensor,wherein the magnetic sensor detects the rotation of the rotation bodythrough the separation shield.
 35. The apparatus according to claim 34,wherein the separation shield is a casing for covering the rotationbody, and wherein the magnetic sensor detects the rotation of therotation body disposed in the casing.
 36. The apparatus according toclaim 34, wherein the rotation body is made of a magnetic material or amaterial including the magnetic material, and has a gearwheel shape. 37.The apparatus according to claim 36, further comprising: anothermagnetic sensor, wherein two magnetic sensors are arranged in parallelso as to separate by a half of pitch of the rotation body andsymmetrically disposed around a rotation axis of the rotation body, andwherein two magnetic sensors output signals, respectively, so that adifferential output signal is obtained.
 38. The apparatus according toclaim 36, wherein the rotation body is a gear connecting to a crankshaftof an engine of a vehicle, and wherein the separation shield is anengine block of the vehicle.
 39. The apparatus according to claim 36,wherein the rotation body is a cam connecting to a camshaft of an engineof a vehicle, and wherein the separation shield is an engine block ofthe vehicle.
 40. The apparatus according to claim 34, wherein therotation body is a cylindrical magnet having a pair of N and S poles,which is alternately disposed on a circumferential periphery of thecylindrical magnet.
 41. The apparatus according to claim 40, furthercomprising: another magnetic sensor, wherein two magnetic sensors arearranged in parallel so as to separate by a half of pitch of therotation body and symmetrically disposed around a rotation axis of therotation body, and wherein two magnetic sensors output signals,respectively, so that a differential output signal is obtained.
 42. Theapparatus according to claim 40, wherein the rotation body is amagnetized rotor mounted on a rotation shaft of a wheel of a vehicle,and wherein the separation shield is a wheel hub of the vehicle.
 43. Theapparatus according to claim 34, wherein the separation shield is madeof non-magnetic material.
 44. The apparatus according to claim 34,wherein the separation shield is a sensor casing for covering themagnetic sensor, wherein the sensor casing is made of magnetic materialand includes an opening, which faces the rotation body, and wherein themagnetic sensor detects the rotation of the rotation body through theopening of the sensor casing.
 45. The apparatus according to claim 44,wherein the sensor casing is made of a permanent magnet.
 46. Theapparatus according to claim 45, wherein the sensor casing has both endsthereof, which open for an outside of the sensor casing, wherein thesensor casing has a sidewall for providing the permanent magnet, andwherein the magnet sensor is disposed in the sensor casing.
 47. Theapparatus according to claim 44, wherein the rotation body is made ofmagnetic material or a material including the magnetic material, and hasa gearwheel shape.
 48. The apparatus according to claim 47, wherein therotation body is a gear connecting to a crankshaft of an engine of avehicle.
 49. The apparatus according to claim 44, wherein the rotationbody is a cam connecting to a camshaft of an engine of a vehicle, andwherein the cam is made of a magnetic material or a material includingthe magnetic material.
 50. The apparatus according to claim 44, whereinthe rotation body is a cylindrical magnet having a pair of N and Spoles, which is alternately disposed on a circumferential periphery ofthe cylindrical magnet.
 51. The apparatus according to claim 44, whereinthe rotation body is a magnetized rotor mounted on a rotation shaft of awheel of a vehicle.
 52. The apparatus according to claim 34, wherein themagnetic impedance device detects a magnetic field in such a manner thatimpedance of the device is changed in accordance with the magnetic filedwhen an alternating current is applied to the device and the impedanceis measured by an external electric circuit, wherein the magneticimpedance device includes a magnetic layer made of Ni—Fe series alloyfilm, wherein the magnetic layer has a length defined as L1 in anenergization direction of the alternating current, a width defined as L2in a perpendicular direction perpendicular to the energizationdirection, and a thickness of the magnetic layer defined as L3, whereinthe ratio of the length and the width is defined as α, i.e., α=L1/L2,and the ratio of the width and the thickness is defined as, i.e.,β=L2/L3, wherein the ratio α is equal to or larger than 10, and theratio β is in a range between 1 and 50, and wherein the width L3 isequal to or larger than 5 μm.
 53. The apparatus according to claim 34,wherein the magnetic impedance device detects a magnetic field in such amanner that impedance of the device is changed in accordance with themagnetic filed when an alternating current is applied to the device andthe impedance is measured by an external electric circuit, wherein themagnetic impedance device includes a magnetic layer made of Ni—Fe seriesalloy film, wherein the magnetic layer has a length defined as L1 in anenergization direction of the alternating current, a width defined as L2in a perpendicular direction perpendicular to the energizationdirection, and a thickness of the magnetic layer defined as L3, andwherein the length L1 is equal to or larger than 100 μm, the width L2 isin a range between 5 μm and 100 μm, the thickness L3 is equal to orlarger than 0.3 μm.
 54. The apparatus according to claim 53, wherein theNi—Fe series alloy film has a composition such that a content of Ni inthe Ni—Fe series alloy film is in a range between 65 wt % and 90 wt %,and/or a content of Fe in the Ni—Fe series alloy film is in a rangebetween 10 wt % and 35 wt %, wherein the Ni—Fe series alloy film has aplurality of grains, dimensions of which are equal to or smaller than100 nm, and wherein the substrate has a surface roughness, which isequal to or smaller than 1300 nm.